*3.2.5. Maturity of bird*

In poultry birds, age is considered for the vaccination of bird; receptors for different pathogens develop in the body of poultry bird at specific ages, so the vaccination is done keeping in view the age of the bird, that is, ND + IB vaccine is done on the first day of birth. Similarly, the Marek's disease vaccine is done immediately after hatching of chicks in the hatchery machine. The IBD (infectious bursal disease/Gumboro) vaccine is done at 10–12 days of birth and booster is given after 10 days. In broiler birds, the hydropericardium syndrome (HPS)/ Angara vaccine is done at 21–23 days of birth. So, the age of the bird is very important for vaccination. The domestic/rural poultry requires injection of ND after every 2–2.5 months.
